Functional decline with aging increases the risk of disability, dependency, falls, and mortality; therefore, there is growing interest in the development of function promoting anabolic therapies (FPTAs) for the treatment and prevention of aging-associated functional limitations. In addition, very limited information is available on how FPATs affect the levels of functional activities (e.g., walking, stair climbing, running, biking, etc.) in the home and community based setting. It has been argued that functional activities in the home environment are an excellent integrated measure of physical function. It is open to further investigation whether administration of FPATs results in clinical benefits measurable at the level of functional activities. In other words, there is a pertinent need for the development of reliable, valid and responsive measures for the assessment of (reduced) level of activity in the evaluation of older individuals participating in clinical trials of FPATs. In general, a thorough understanding of functional limitations in older Americans requires the continuous measurement of functional activities as well as environmental constraints in the home and community based setting. Previous work by our research group has demonstrated that functional activities in the home and community based setting lasting longer than 5 seconds can be accurately and reliably assessed with an Activity Monitor (AM;2,3). The advantage of the AM compared to questionnaires is that it allows for continuous assessment of functional activities, which will improve the responsiveness to treatment effects. However, its current design has a number of limitations related to maximal hours of date recording, energy supply, the extraction of recorded date, the size of the data-logger attached to the body, the algorithms used in data-reduction and the assessment of environmental barriers (see Section 2: Background, Previous Research and Significance).